The present invention relates to filtering systems having over-voltage protection apparati. More particularly, the present invention relates to filtering systems having over-voltage protection apparati with a circuit breaking feature. Even more particularly, the present invention relates to an input/output filtering system having a tri-modal form of over-voltage protection in an apparatus with corresponding tri-modal disconnect features.
The current state of the art electronic components (e.g., both commercial and residential computers and related equipment) accommodate transient voltage surge suppression features for protecting their highly sensitive circuits from over-voltage damage. Most transient voltage surge suppression systems today, in particular, input/output filtering systems for audio/video systems, address only minor fault conditions associated with normal use and cannot handle a major over-voltage condition as would occur during loss of neutral, loss of ground, or repetitive current pulses (e.g., from a lightning strike). Typical voltage surge protection devices comprise a plurality of fault fuses where the input is disconnected from the output. The related art surge suppression systems may involve various metal oxide varistor (MOV) and fuse combinations. MOVs are ceramic materials (e.g., ZnO grains in combination with an amorphous material). MOVs maintain the voltage within a narrow band (i.e., varistor voltage) over a wide current range. During major over-voltage conditions, the MOVs may absorb heat so excessive such that they will rupture or explode, thereby allowing the related electronic equipment to be destroyed.
Some related art surge suppression system patents include:
(1) U.S. Pat. No. 5,153,806 to Corey which teaches a plurality of parallel pairs of MOVs, each pair being in series with a thermal fuse, a pair of parallel resistors, and a capacitor in parallel with a resistor;
(2) U.S. Pat. No. 5,896,265 to Glaser et al. which teaches a surge suppression of radio frequency transmission comprising a solid state discharge device in series with an inductor and a resistor;
(3) U.S. Pat. No. 5,914,662 to Burleigh which teaches a plurality of serially coupled MOVxe2x80x94thermal fusexe2x80x94resistor combinations, each combination in parallel with one another, and an LCD display;
(4) U.S. Pat. No. 5,388,021 to Stahl which teaches a plurality of MOVs being in parallel with a plurality of resistors and a plurality of inductors, and a plurality of MOVs being in parallel with another;
(5) U.S. Pat. No. 5,757,603 to Kapp et al. which teaches a plurality of silicon avalanche diodes in series with a thermal fuse;
(7) U.S. Pat. No. 4,739,436 to Stefani et al. which teaches two MOVs in combination with a fuse and an indicator light;
(8) U.S. Pat. No. 5,537,044 to Stahl which teaches an MOV serially coupled with a gas tube, an inductor, a parallel resistor-inductor combination, the serial coupling in parallel with another MOV;
(9) U.S. Pat. No. 5,617,288 to Zaretsky which teaches a signal adjuster coupled to parallel resistors in series with an amplifier in series with an MOV; and
(10) U.S. Pat. No. 5,8032,946 to Misencik et al. which teaches parallel resistors in series with a thermal fuse with a green indicator light and a red indicator light.
A typical problem associated with these related art inventions is that an electrician may accidentally reverse the line wire and the neutral wire, creating an extremely hazardous situation at the wall receptacle, even if the invention succeeds in disconnecting the circuit to a peripheral device. In addition, the related art patents maintain an inordinately high component count to achieve their purpose of surge suppression. Therefore, a need exists for a circuit apparatus and a method which prevent (1) the hazardous condition occurring at the wall receptacle, arising from accidental reversal of the line wire with the neutral wire, from adversely affecting at least one peripheral device in the line, and (2) the overheating and destruction of MOVs in an over-voltage protection circuit by providing an efficient circuit configuration (i.e., the minimum number of components for device size reduction) which assures a rapid simultaneous disconnect of both the hot line and the neutral line.
An object of the present invention is to provide an apparatus and a method which prevent (1) the hazardous condition occurring at the wall receptacle, arising from accidental reversal of the line wire with the neutral wire, from adversely affecting at least one peripheral device in the line, and (2) the overheating and destruction of MOVs in an over-voltage protection circuit by providing an efficient circuit configuration (i.e., the minimum number of components for device size reduction) which assures a rapid simultaneous disconnect of both the hot line and the neutral line.
Another object of the present invention is to provide an apparatus and a method which prevent (1) the hazardous condition occurring at the wall receptacle, arising from accidental reversal of the line wire with the neutral wire, from adversely affecting at least one peripheral device in the line, and (2) the overheating and destruction of MOVs in an over-voltage protection circuit by opening the circuit to simultaneously disconnect both the hot line and the neutral line feeding a load when the over-voltage event occurs in any of the three following wire pairings: hot line to neutral line (L-N), hot line to ground line (L-G), or neutral line to ground line (N-G).
Yet another object of the present invention is to provide a flexible system for use with audio/video equipment which provides input/output filtering in conjunction with tri-mode over-voltage protection and disconnect.
Accordingly, the present invention provides an input/output filtering system for use with audio/video systems having a tri-mode over-voltage protection and disconnect circuit apparatus for all AC power wires/lines and combinations thereof. The hot line (L), neutral (N), and ground (G) wires are all paths vulnerable to destructive high voltages. In particular,e the present invention provides an apparatus and a method which prevent (1) the hazardous condition occurring at the wall receptacle, arising from accidental reversal of the line wire with the neutral wire, from adversely affecting at least one peripheral device in the line, and (2) the overheating and destruction of MOVs in an over-voltage protection circuit by providing an efficient circuit configuration which assures a rapid simultaneous disconnect of both the hot line and neutral power lines. The present invention achieves this by opening the circuit to simultaneously disconnect both the hot line and the neutral line feeding a load when the over-voltage event occurs in any of three wire pairings: hot line to neutral line (L-N), hot line to ground line (L-G), or neutral line to ground line (N-G).
By example, in a single phase AC power system, the hot line (L), the neutral line (N), and ground line (G) are all paths vulnerable to destructive high voltages. The present invention system maintains an apparatus which protects these paths by first providing protection devices in the form of metal oxide varistors (MOVs) in parallel for each pair of wires (i.e., hot line to neutral, hot line to ground, and neutral to ground). The apparatus additionally comprises in-line fuses and a normally open relay device that disconnects both the hot line as well as the neutral line from the load. The MOV devices are activated by an over-voltage condition and upon absorbing all the extra and potentially damaging power surges and over-voltages which cause excessive current to flow, which then opens the fuse, causing de-energizing of the relay device.
Accordingly, in the event of a sufficiently high voltage (i.e., VL-N greater than 120V to 130V), from hot line-to-neutral or hot line-to-ground, causing excessive heating of the MOV protection devices, the hot line and neutral line will be disconnected from the user""s connected equipment. This disconnect is facilitated by the use of an open circuit condition of the in-line special fuses which causes de-energizing of the relay device and reversion of the relay contacts back to a normally open condition. Preferably, this is a non-resettable disconnect condition that maintains the relay in its normally open condition, especially where the over-voltage protection circuit is the final protection to the connected equipment for preventing excessive current and heating which, otherwise, would lead to smoke and/or fire. In the preferred embodiment, the relay simultaneously disconnects the hot line as well as the neutral line from the connected peripheral equipment (i.e., the load) such as audio and visual devices.
The current through the line may be denoted by LL. The current through an MOV, IMOV, must remain less than the rated current for the MOV, IMOV-rated, in normal operation. During an over-voltage event where the current through the MOV exceeds its current rating (i.e., IMOV greater than IMOV-rated), thereby effecting a current through the thermal fuse greater than its current rating (IL=ITF, ITF greater than ITF-rated), such thermal fuse will open, thereby preventing voltage application at the relay, thereby preventing the relay from being energized, and thereby effecting its normally-open contact state (See FIG. 1).
In all the foregoing protection modes (i.e., L-N, L-G, N-G), a warning feature may be provided which indicates that a protection device (e.g., an MOV) has absorbed excessive energy, thereby opening a thermal fuse which effectively opens the path to any protection device. The warning feature may continue to alert the user even if power is no longer applied to the equipment. This warning feature alerts the user of the otherwise potentially destructive event. Upon so alerting the user, the apparatus should be unplugged from the wall outlet and replaced. The warning feature may be audio and/or visual in nature.
The present invention further employs an input filter disposed forward and a plurality of output filters disposed aft of the tri-mode protection apparatus. The input filter slows the rise-time of an incoming transient so that the tri-mode protection device response time is not exceeded and reduces noise in the line. The output filter performs the functions of removing noise which back-creeps into the line from a peripheral device (e.g., radio frequency noise). The present invention further comprises a plurality of MOV-thermal fuse sets disposed between each output filter and peripheral device for individually isolating noise from each peripheral device of a plurality of such devices disposed on a line by subjecting such noise to different filters (e.g., analog, video, digital). Thus, any back-emitted noise is filtered, and thus, highly attenuated, thereby preventing interference among a plurality of peripheral devices on the line. A plurality of isolation transformers may be disposed forward and in series with each output filter and may be electronically coupled with the hot line. Such filtration is applied to that which travels through an Internet line as well as through a basic power line. Other features of the present invention are disclosed, or are apparent in the section entitled xe2x80x9cDETAILED DESCRIPTION OF THE INVENTION.xe2x80x9d